This invention relates generally to golf balls and, in particular, to a geodesic pattern for arranging dimples in an outer spherical surface of a golf ball.
Dimples provide golf balls with important aerodynamic characteristics. For example, dimples create a blanket of air turbulence around a golf ball which reduces drag and thereby increases distance. Dimples also enhance lift as a golf ball spins in a backward direction after being struck by a golf club. When a golf ball is backspinning, the dimples improve air flow above the golf ball thereby resulting in increased air pressure below the golf ball which enhances lift.
It is known that lift and drag can be altered by arranging the dimples in different geodesic patterns such as icosahedrons, octahedrons and dodecahedrons. If lift is increased, a golf ball has a higher trajectory. If drag is reduced, a golf ball travels farther. A proper combination of lift and drag gives satisfactory performance.
Presently, two types of golf balls are most common. Three-piece golf balls have a small core around which windings are wrapped, and a cover in which dimples are formed. Two-piece golf balls have a large core with no windings, and a cover with dimples formed therein. A further aerodynamic characteristic of a golf ball is spin rate which is determined by cover hardness relative to core hardness. Generally, three-piece golf balls have a higher spin rate than two-piece golf balls. Therefore, a particular dimple pattern may result in satisfactory performance on a three-piece golf ball but unsatisfactory performance on a two-piece golf ball.
Geodesic dimple patterns for golf balls have many variations. One conventional dimple pattern is the icosahedron wherein dimples are arranged in twenty triangular regions. A perfect icosahedral dimple pattern is disclosed in British Specification No. 377,354 to Pugh. Since most commercially available golf balls have a cover constructed with a straight seam or parting line lying on an equator of the golf ball, a problem exists in that the icosahedral pattern disclosed by Pugh is interrupted at the equator. The straight seam or parting line results from a conventional molding process used in making golf balls. U.S. Pat. No. 4,653,758 to Karsten Solheim solves this problem by disclosing a method of making a golf ball wherein the cover has a seam that passes back and forth across the equator of the golf ball and thus does not interrupt the Pugh dimple pattern.
A golf ball should also have what is referred to as "spherical symmetry" by the United States Golf Association (USGA). Spherical or aerodynamic symmetry is determined by launching a golf ball so that it spins about one axis and then launching the same golf ball so that it spins about another axis. Any differences in length of flight (i.e. carry) and time of flight are noted. In order to conform to the USGA Rules of Golf, these differences must not be more than three yards for carry or greater than 0.20 seconds for flight time. Changing the dimple pattern on a nonconforming golf ball may make it aerodynamically symmetrical.
A need exists for an improved geodesic dimple pattern for use primarily on, but not limited to, two-piece golf balls having a cover constructed in accordance with the aforementioned Solheim patent.